Liquid injection pump



Sept. 29, 1942. w, vo 2,297,511

LIQUID INJECTION PUMP Filed Dec. 3, 1940 xlflor-nev Patented amt, 1942 UNITED. STATES PATENT OFFICE A i i I mourn ii'r onrum.

Application December a, 1940, Serial No. 368,316

InG

ermany December 23, 1939 Claims. I (0!. 103-41) The invention relates to liquid injection pumps, as for instance fuel injection pumps for internal combustion. engines, of the-reciprocable plunger type having a relief port for relieving the pressure on the liquid in the compression space of the pump cylinder after delivery of liquid therefrom. More particularly, it relates to pumps of this kind having an annular groove in that part of the cylinder near the beginning of its compression space, in which the compression pressure on the liquid therein is developed and maintained and from discharged.

The primaryobject of the invention is to reduce leakage losses in pumps of this kind byproviding cooperative means in the piston and cylinder for sealing the compression space at the annular groove and also at a separated but communicating place during substantially the entire movement of the piston through the compression space.

Other objects and advantages will be understood from the following description taken in connection with the accompanying drawing for fuel injection pumps, in which, 1

Figure 1 is a partial view of an injection pump of known type provided with suction bores in the cylinder wall;

Fig. 2, a partial view of an injection pumpof known type provided with an annular groove instead of suction bores;

Fig. 3, a sectional view of a pump according to the invention; and

Fig. 4 is a diagram which illustrates the rela tion between speed of travel of a pump piston' which the liquid is r The delivery characteristic will be flatter if the suction bores c are replaced by an annular groove, as indicated in Fig.2. In this instance, shortlybefore' the annular groove c is covered by the peripheral surface of the piston near the top surface thereof, there exists a gap effective even at high speeds owing to'thecircumferential length remaining for the escape of fuel from the compression space without much throttling until the gap iscompletely closed. The provision ofan annular groove of this kind involves, however, the disadvantage of greater leakage losses than in a pump having plain suction bores as shown in Fig. 1 with the result that the and the output or delivery of the fuel oil, in

volume, during the delivery stroke, the ordinates indicating output and the abscissae indicating speed. Each of the lines A, B and 0 gives what is called the delivery characteristic of the respective pump, identified hereinafter.

In a pump of known type as shown in Fig. 1

the piston thereof controls one or more suction bores c in the cylinder wall. Even in case of constant adjustment of the regulating mem-' cylinder more flatly than the line delivery characteristic of a pump such as shown in Fig. 2, if such pump be dimensioned and adiusted like the pump of Fig. 1, corresponds to.

- surface of the piston, the recess being such as to keep said channel in communication with the.

fuel supply during the first part of the pressure, or delivery stroke, at least up to the time when the piston closes the said annular groove.

One form of,the invention is illustrated in Fig. 3. This arrangement gives a delivery characteristic approximating line C, in Fig. 4, which is morefavorable with respect to the quantity delivered than line B and extends, moreover,

shown in Fig. 1.

position is designated .a in'Figs. 1 to 3; while b is the cylinder liner and 0 refers to the suction or inlet bores or ports. At the upper dead center position of the pistontthe top surface d thereof is level with the dash-and-dot line I. In the construction shown in Fig. 3 a suction bore c communicates atthe lower dead center position shown throughan annular groove e'in the pistonsurface, a bore 1, and a longitudinal channel 9 in the wall of the cylinder liner b, V with an annular groove h in the interior surface of the .liner. A recess It partly limited by an inclined edge i in the piston surface is continually in communication with the pump space 0 through a cross-channel m and a longitudinal bore 11. in the piston a. The inclined edge 1' con-- trolsthe return flow channel or relief port p inthewell known way. The top of the cylinder A of the known pump liner 17 inserted in a pump casing q supports a guide member 1' for a pressure valve s whose guide stem at the end adjacent the valve cone has the form of a discharge piston t in the delivery part of the pump.

Proceeding from the position shown in Fig, 3 at which the pump chamber is filled with fuel, the piston a, during the first part of its compression stroke, drives the displaced fuel through the annular groove 12., the connecting channel 9, the bore 1 and the annular groove e of the piston back into the suction pipe. However, when the control edge (1 of the piston a has reached the upper edge of the annular groove h which is the beginning of the compression space in the cylinder, pressure rises therein until the pressure valve s is lifted. As soon thereafter as the piston of the valve 3 emerges from its guide, the fuel is forced into the pressure pipe (now shown) connected to the delivery part of the pump until the inclined edge 12 of the recess is in the piston a opens up the return channel p in the liner b. At this moment the pressure in the compression space is reduced, the pressure valve s closes, and the discharge piston it moves into its guide which increases according to its volume the volume of the pressure pipebeginning below the valve seat and leading to the nozzle in the engine cylinder, to thereby relieve this pipe after each injection therethrough. The fuel displaced from the pump space during the last part of the compression stroke is returned to the relief port 1) through the channels 11. and m and the recess is of. the piston a. N

If a spring loaded ball or check valve, instead of the pressure valve s, is provided in the pressure pipe, it is preferable to let the covering of the cross channel by the piston a follow as quickly as possible that of the annular groove h, so that leakage losses through the annular groove cannot go farther than to the covering of the channel 1. The leakage losses are thus considerably decreased. On the other hand, when a pressure valve fitted with a discharge or relieving piston is employed, the control may be such that the channel f is closed only shortly before the discharge piston emerges from its guide.

Due to the provision of the connecting channel g and the bore 1 besides the annular groove h, leakage losses, particularly in the lower and medium speed ranges, are considerably decreased compared with a pump of the type shown in Fig. 2, as indicated by a comparison of curves C and B, Fig. 4.

What is claimed is:

1. In a liquid pump; a cylinder which has suction, delivery and relief ports, and also which has an annular groove located at the beginnin of its compression space and a longitudinal channel communicating with said groove; anda piston which is reciprocable in said cylinder and has means cooperative with said suction and relief ports at different points of its compressionstroke to first compress the liquid in said compression space for discharge therefrom to the delivery port and to then relieve the compression pressure in said space, and also which has means for sealing said annular groove and for sealing said longitudinal channel-at a place separated from said annular groove during substantially the entire movement of the piston through said compression space.

2. In a liquid pump; a cylinder having suction, delivery and relief ports, and also having an annular groove located at the beginning of its compression space with a longitudinal channel communicating therewith; and a piston which is reciprocable in said cylinder with its end surface arranged to seal said annular groove, and also which has ineans cooperative with said suction and relief ports at different points in its compression stroke to first compress the liquid in said compression space for-discharge therefrom to the delivery port and to then relieve the compression pressure in said compression space, and also which has means for sealing said longitudinal channel at a place separated from said annular groove at substantially the point in its compression stroke at which said end surface seals said annular groove.

' 3. In a liquid pump; a cylinder which has suction, delivery and relief ports and which also has an annular groove located at the beginning of its compression space with a longitudinal channel communicating therewith; and a piston which is reciprocable in said cylinder and has a longitudinal bore arranged to establish communication between said suction port and said annular groove by way of said longitudinal channel, and also which has means to seal said annular groove and said longitudinal channel at a place separated from said annular groove to hereby seal said compression space at two separated places, and also which has means for establishing communication between said relief port and said compression space to relieve the compression pressure in said space.

4. In a liquid pump; a cylinder having suction, delivery and relief ports, and also having an annular groove located at the beginning of its compression space and communicating with a a longitudinal channel; a piston which is reciprocable in said cylinder with its end surface arranged to seal said annular groove, and also which has means cooperative with said suction and relief ports at different points in its compression stroke to first compress the liquid in said compression space for discharge thereof to the delivery port and to then relieve the com pression pressure in said space, and also which has means for sealing said longitudinal channel at its end distant from said annular groove to thereby seal said compression space during substantially the entire movement of the piston therethrough; and a fluid controlled pressure valve located near said delivery port and arranged to open upon development of a predetermined pressure in said compression space; said piston being arranged to close the distant end of the longitudinal channel after closing said annular groove but shortly before said pressure valve fully opens.

5. In a fuel pump, a cylinder having an annular groove located at the beginning of its compression space, a longitudinal channel communicating with said annular groove and opening into the cylinder at a point remote from the compression space, a suction port opening into the cylinder adjacent the opening to said longitudinal channel, a relief port opening into the cylinder beyond the suction port,,and a delivery port connected to the cylinder at the end opposite the annular groove, of a valve arranged to close said delivery port, and a piston reciprocable in said cylinder, said piston having an end surface arranged to come outside the annular groove, at the end of the suction stroke of the piston, and a peripheral surface arranged to fit the compression space of the cylinder and gradually close the communication between the annulerrgroove and said 'eompression space after second recess oerried by the plston and arranged the beginning of-the inward stroke-of thepisto-put the lofigltudlnal channel in communicaton, said piston having a peripheral recess artion with the suction port near the end 0f the ranged to come opposite the relief port as the suction stroke and while the piston unclosespump approaches the end of its inward or com-- 5 the annular groove.

presslon stroke, a longitudinal boreconne'ctn'ng WILLY the compression space with said recess, and a r 

